Jordan Poyer came up with three interceptions, and Sean Mannion threw for 270 yards and a touchdown, as 14th- ranked Oregon State downed Washington State, 19-6, at Reser Stadium.
Markus Wheaton had 95 yards receiving and a touchdown for the Beavers (4-0, 3-0 Pac-12), who also got a pair of field goals from Trevor Romaine. Brandin Cooks contributed five catches for 82 yards.
With the victory, Oregon State surpasses their three-win total from last season and improves to 4-0 for the first time since the 2002 season.
"I am really proud of the players. Today it was relatively low scoring with both defenses playing well," Oregon State head coach Mike Riley said. "I really couldn't be prouder of our defense. That is going to be really important moving forward, that everybody picks each other up and that we find that way to win. Defensively, we made a lot of plays."
Washington State quarterback Connor Halliday had a rough game, going just 9- of-20 passing for 81 yards and three interceptions. His replacement, Jeff Tuel, went 11-of-17 for 126 yards and an interception, and also was sacked three times.
"Defenses for both teams played better than the offenses," said Washington State head coach Mike Leach. "Oregon State's defense was more physical than our offense. Their defense got our offense out of timing on a lot of plays."
Gino Simone caught three balls for 83 yards and Andrew Furney connected on two field goals for the Cougars (2-4, 0-3).
Up by seven points late in the fourth quarter, a 1-yard touchdown run by Tyler Anderson with 4:27 left padded the Beavers' lead.
After Washington State went three-and-out following the opening kick, the Beavers took advantage of good field position to get on the board. Starting from their own 45, the offense took the ball down to the Cougars' 14-yard line, but had to settle for a 30-yard field goal from Romaine to take a 3-0 lead.
Oregon State got the ball right back when Halliday threw a pick on 3rd-and-10 to Poyer at the Washington State 32-yard line. After moving the ball to the 24, however, the Cougars came away empty when Mannion threw an incomplete pass on 4th-and-2 for a turnover on downs.
The Beavers defense played strong the next two Cougar possessions, forcing punts each time.
Washington State finally moved the ball downfield early in the second quarter, getting a 1st-and-goal from the 5-yard line, but the Beavers forced a 24-yard field goal by Furney to tie the game, 3-3, with 9:08 left in the first half.
Romaine added another field goal for Oregon State at the 2:51 mark, and the Beavers went into the half leading, 6-3.
Oregon State received the kick in the second half, and immediately increased their lead by marching 75 yards on 10 plays, capping the drive with a 12-yard touchdown pass to Wheaton for a 13-3 edge.
Poyer had another interception on Washington's ensuing possession, but the Beavers gave the ball right back at Washington State's 18-yard line when Mannion was picked off by Casey Locker with 6:34 left in the third.
Tuel, playing for a benched Halliday, orchestrated the Cougars' only other scoring drive of the day, putting together a 9-play sequence in the fourth quarter that set up a Furney field goal with 9:33 left to play to make it a 13-6 game.
The Beavers' four-game win streak is their longest since the 2009 season when defeating UCLA, California, Washington and Washington State...The Beavers' defense held Washington State from scoring a touchdown. Oregon State last kept a team out of the end zone when shutting out Pittsburgh in the 2008 Sun Bowl ... Poyer's three interceptions make him the first OSU player with multiple interceptions since he had two against Arizona State in 2011. His three interceptions in one game are tied for second-most in school history and is the most since Mitch Meeuwsen tallied three against Washington State on Oct. 25, 2003 ...The No. 14 ranking is the highest since the Beavers were No. 13 Nov. 29, 2009.